Of course. And the first computer wargames were extremely simple as a result. Stuff like Empire (from 1977), for example. So how vital it is to use the full cap

Of course. And the first computer wargames were extremely simple as a result. Stuff like Empire (from 1977), for example. So how vital it is to use the full capacity of the computer depends on the computer and on the game you want to run on it. But even Empire spends most of its time waiting for user input.